feat: configure automatic refresh when declaring computed columns (#4607)

Add `auto_refresh_enabled` and `auto_refresh_interval_seconds` to the
Rust builder and Python sync/async add-column APIs for computed columns
and registered Function outputs.

Python users can configure refresh when declaring a column:

```python
table.add_columns(
    computed={"total": "price * quantity"},
    auto_refresh_enabled=True,
    auto_refresh_interval_seconds=300,
)
```

Omit the interval to let the server determine when to refresh:

```python
table.add_columns(computed={"discounted_total": "total * 0.9"})
```

The async API accepts the same options:

```python
await async_table.add_columns(
    computed={"total": "price * quantity"},
    auto_refresh_enabled=True,
    auto_refresh_interval_seconds=300,
)
```

For an existing registered `FunctionApplication`, the options also apply
to Function columns. Disabling automatic refresh still permits explicit
refresh:

```python
table.add_columns(
    {"features": function_application},
    auto_refresh_enabled=False,
    auto_refresh_interval_seconds=300,
)
table.refresh_column("features")
```

Options apply to every output declared by a call. Automatic refresh is
enabled by default; when the interval is omitted, the server determines
when to refresh. An explicit interval sets a minimum delay after a
successful refresh. The interval does not force recomputation of
unchanged inputs. Invalid intervals and options on one-time transforms
are rejected before declaration.

Native declarations persist `computed_column.auto_refresh_enabled` and
an explicitly supplied `computed_column.auto_refresh_interval_seconds`
in each output field’s metadata in the same commit as the declaration.
An omitted interval is neither stored nor sent in remote requests.
Remote declarations forward the settings to Cloud/Enterprise servers.
Local tables store these settings; automatic execution requires a
supporting server with scheduling enabled.

docs/web/sql/ddl/table.mdx

@@ -51,6 +51,43 @@ The column is committed empty and the expression is stored, not evaluated:
 declaring one on a billion-row table costs what declaring one on an empty table
 costs. [`REFRESH COLUMN`](/sql/dml/refresh) fills it.
 
+{/*
+Draft for automatic computed-column refresh. Enable this section when the
+server feature is released.
+
+### Automatic refresh options {#automatic-refresh-options}
+
+```sql
+ALTER TABLE t ADD COLUMN doubled AS value * 2
+WITH (auto_refresh_enabled = true, auto_refresh_interval_seconds = 300);
+
+ALTER TABLE t ALTER COLUMN doubled SET auto_refresh_enabled = false;
+ALTER TABLE t ALTER COLUMN doubled SET auto_refresh_interval_seconds = 600;
+ALTER TABLE t ALTER COLUMN doubled SET auto_refresh_enabled = true;
+```
+
+Automatic refresh is enabled by default. An explicitly configured interval is
+stored in each computed output's field metadata; when omitted, the server
+determines when to refresh. The interval must be a positive integer
+and is minimum pacing after a successful refresh of that output; unchanged
+inputs do not force work. A new column is immediately eligible for its first
+refresh. The server's separate automatic-refresh switch must also be enabled.
+
+These options also work beside a Function binding's `version` and `branch`:
+
+```sql
+ALTER TABLE t ADD COLUMN (label, score) AS classify(text)
+WITH (version = 'fv_1', auto_refresh_enabled = true,
+      auto_refresh_interval_seconds = 300);
+ALTER TABLE t ALTER COLUMN score SET auto_refresh_enabled = false;
+```
+
+Declaration settings initialize every output in the group; later SET commands
+change one output. Disabling automatic refresh prevents new submissions while
+allowing inflight jobs to finish and explicit REFRESH COLUMN to run. Column
+SUSPEND/RESUME syntax is not supported.
+*/}
+
 {/*
 Draft for the Functions release.
 
@@ -81,12 +118,14 @@ ALTER TABLE t ADD COLUMN (label, score) AS classify(text) WITH (version = 'fv_1'
 
 ```sql
 ALTER TABLE t ADD COLUMN c AS f(x) FILTER (WHERE keep) WITH (version = 'fv_1')
-ALTER TABLE t ADD COLUMN c AS f(x) WITH (num_workers = '2')
+REFRESH COLUMN c ON t WITH (num_workers = 2)
 ```
 
 <Note>
-`WITH` on a plain computed column accepts only `version`. Resource options such
-as `num_workers` apply to function columns, where there are workers to size.
+Declaration `WITH` accepts `auto_refresh_enabled` and
+`auto_refresh_interval_seconds`. Function bindings also accept `version` and
+`branch`. Worker resource options such as `num_workers` belong on
+`REFRESH COLUMN ... WITH (...)`.
 </Note>
 */}